I have a 1999 Doge Ram 2500 with a cummins deisel and an automatic transmission. It has been having problems upshifting while the lever is in the (D) position.. About half the time you have to aid it by shifting to nuetral and back to (D) drive again. Problem intialy started going to drive to overdrive, now it pretty much happens in all gears. Just found out that when the lever is in 2nd gear position it will not go into second gear it stays in 1st, so moving shift from 1st to 2nd makes no difference. It will shift into second with lever in drive position either by itself or being aided by shifting lever to nuetral and back to drive again. Sometimes just letting gas off will let it shiftwhen RPM's are up. Shop said trany is slipping but it does not seem like any other tranny that I have experienced slipping with. It seems like its having a problem upshifting.

Need help. Thanks

 

Diesel trans don't shift like the other transmissions, Depends on weather temp your transmission will start in 2nd gear. But if you are having upshifting problem from 2nd to 3rd or 4th, the seals inside the transmission maybe hard and leaks fluid pressure, the only fix is an overhaul kit with seals.Be sure to ck you fluid level 1st .